Cascading style sheets (CSS) provide web site developers with control over the visual appearance, style (e.g., size, color, font, margins, borders, backgrounds, etc.), and positioning of text in web pages without compromising the structure of the page. Developers may use CSSs to create templates for attaching style properties and rules to structured documents (e.g., hypertext markup language (HTML) documents and extensible markup language (XML) applications). CSSs separate the presentation style of documents from document content thereby simplifying web authoring and site maintenance. CSSs may include instructions in the code of a web site that describe how a browser should render any instance of a particular element on a page. For example, style sheets can provide instructions for how all of the hypertext, headers, links, or text should appear.
The style sheets are referred to as cascading because multiple style sheets can be applied to the same web page. The style of a web page may be rendered from multiple sources with an established order of precedence where the definitions of any style element conflict. For example, some text may be rendered in accordance with properties defined for a first style rule. The text may be rendered in accordance with a hierarchical arrangement of other style rules that include properties that are not defined for the first style rule.